In constrained environments, such as engine environments, it is known that the transmission of fluids such as gas, oil or fuel may sometimes be difficult to achieve by means of conventional supply conduits formed of one or more round section tubes. Indeed, an engine environment imposes numerous mechanical constraints such as a cramped space, imposed displacements, installation tolerances or instead thermal stresses that prevent the crossing of round section tubes. For these reasons, it is known, in engine environments, to use conduits formed of oval section tubes which have the benefit of offering reduced bulk in one of the dimensions of the tubes. In comparison to a round section tube, and with surface area of equivalent section, the oval geometry of oval section tubes makes it possible to transport a fluid in a restricted space on one axis.
However, oval section tubes, also called oblong section tubes, have an unequal distribution of pressure forces within the tube. Indeed, on account of the disparity of the dimensions of an oblong section tube, the pressure forces are not distributed uniformly over the whole surface of the tube, which generates stresses varying by a factor comprised between 1 and 10 within the tube. Yet, too high stresses in a tube may lead to deterioration or even rupture of the tube.
To compensate this disparity of stresses within an oblong section tube and to consolidate the oblong section tube, certain manufacturers propose inserting each oblong section tube in ring type stiffeners. However, the putting in place of an oblong section tube in ringed stiffeners is complex, in particular in a restricted environment, and thus expensive.
Other manufacturers propose, to compensate the disparity of stresses within an oblong section tube and to consolidate the tube, housing stiffeners—called internal stiffeners—inside the oblong section tube. However, such a solution requires the implementation of a planned cutting method which has the drawback of being particularly expensive. Moreover, the internal stiffeners are positioned in the path of the fluid, which generates head losses.
Another solution proposed by manufacturers is to produce oblong section tubes, the section of which has a variable thickness. Such tubes, manufactured by addition of material, require finishing phases of which the cost is relatively high.
Generally speaking, an oblong section tube may conventionally be formed of a curved metal or alloy plate, the edges of which are welded to each other to form the oblong section tube. Indeed, circular section tubes, called rolled tubes, are welded with a weld bead then the oblong section is obtained by crushing. An oblong section tube may also be formed of two half-shell plates manufactured separately and assembled by welding of the edges together. However, whether there is a single weld or two welds, the welding zone of the edges constitutes a line—or two lines—of least resistance inducing reductions in the mechanical characteristics. The implementation of such oblong section tubes is thus relatively costly.